They changed it. They changed Incredibox Demo and I didn't realise. I haven't played it in a while, so I don't know how long this was the case. I mean, I've always wanted to play the official version of Wekiddy instead of UhohStinky's scratch version, but now those who can't afford the app only have this to play. I guess the Incredibox team just intended to use the final bonus of Wekiddy as a sort of "advertisement" for the rest of the game, which I'm taking from the fact that it has references to most of the other versions. Shout out to @testerbob31 because he likes Incredibox as well, and probably knows more about it than I do.
